Embodiments of the invention relate to rocket engines. More particularly, embodiments of the invention relate to the cooling of rocket engines.
When in operation, rocket engines generate a significant amount of power in the form of heat. In order to keep a rocket engine from melting while maintaining high efficiency, a cooling system using one of the propellants is often incorporated into the engine. It is the job of the cooling system to maintain engine structural integrity while recycling the energy lost to the walls of the engine. This approach is called regenerative cooling because the heat absorbed by the coolant/propellant is eventually returned to the engine. In cooling a rocket engine the biggest challenge is in maintaining reasonable wall temperatures around the area of the throat. This is because the amount of heat that needs to be removed from the region of the throat, per unit surface area, is quite large compared to the rest of the engine. This region is often cooled by forced convection, a scheme that involves forcing the coolant through small channels located in the wall of the engine. This method typically requires a great deal of pressure. In some engines this pressure is obtained at the expense of engine performance.
Embodiments of the invention include a rocket engine having a combustion chamber with a chamber inner wall, a throat with a throat inner wall, and a nozzle with a nozzle inner wall. The chamber inner wall is a vacuum plasma sprayed, the throat inner wall is the vacuum plasma sprayed metal, and the nozzle inner wall is the vacuum plasma sprayed metal. A porosity of the vacuum plasma sprayed metal varies in an axial direction of the engine.
The variable porosity is designed to act for both structural considerations and as a pressure distribution manifold, capable of delivering a known pressure drop, and thus flow, within the variable porosity area.
Embodiments of the invention include a rocket engine having a combustion chamber with a chamber inner wall, a throat with a throat inner wall, and a nozzle with a nozzle inner wall. The chamber inner wall is a vacuum plasma sprayed metal, possibly porous to allow transpiration cooling, the throat inner wall is a vacuum plasma sprayed metal having a variable porosity in the axial direction to allow specific transpiration cooling in this area of increased heat flux, and the nozzle inner wall is a vacuum plasma sprayed metal, possibly porous to allow transpiration cooling as well.
Other embodiments of the invention include methods of fabricating a rocket engine. An example of such a method includes vacuum plasma spraying a first metal onto a throat region of a mandrel to form a throat inner wall, vacuum plasma spraying the first metal onto a combustion chamber region of the mandrel to form a chamber inner wall, and vacuum plasma spraying the first metal onto a nozzle region of the mandrel to form a nozzle inner wall. A second metal is vacuum plasma sprayed onto the throat inner wall, the chamber inner wall, and the nozzle inner wall to form an intermediate layer. A cooling channel is formed in the intermediate layer and the cooling channel is filled with a removable material. A third metal is vacuum plasma sprayed onto the intermediate layer and the removable material to form a closeout layer and the removable material is removed. A porosity of the first metal varies in an axial direction of the engine.
Other embodiments of the invention include methods of cooling a rocket engine. An example of such a method includes passing a coolant through a cooling channel, passing the coolant from the cooling channel to a porous throat inner wall of the engine, and passing the coolant through the throat inner wall to a throat of the engine by transpiration. The coolant passing through the cooling channel cools a combustion chamber inner wall of the engine by convection and a nozzle inner wall of the engine by convection. The coolant passing through the throat inner wall cools the throat by transpiration. The combustion chamber inner wall is formed by vacuum plasma spraying, the nozzle inner wall is formed by vacuum plasma spraying, and the throat inner wall is formed by vacuum plasma spraying. A porosity of the vacuum plasma sprayed metal varies in an axial direction of the engine.